THE VIRULENCE GENE-CLUSTER OF LISTERIA-MONOCYTOGENES IS ALSO PRESENT IN LISTERIA-IVANOVII, AN ANIMAL PATHOGEN, AND LISTERIA-SEELIGERI, A NONPATHOGENIC SPECIES

Most known Listeria monocytogenes virulence genes cluster within a 9.6 -kb chromosomal region. This region is flanked on one end by two uncha racterized open reading frames (ORF A and ORF B) and ldh, an ORF presu mably encoding the L. monocytogenes lactate dehydrogenase (J.-A. Vazqu ez-Boland, C. Kocks, S. Dramsi, H. Ohayon, C. Geoffroy, J. Mengaud, an d P. Cossart, Infect. Immun. 60:219-230, 1992). We report here that th e other end is flanked by prs, an ORF homologous to phosphoribosyl PP, synthetase genes. ORF B and prs were detected in all Listeria species and thus delimit the virulence region. This virulence gene cluster wa s detected exclusively in hemolytic Listeria species, Listeria ivanovi i, an animal pathogen, and Listeria seeligeri, a nonpathogenic species .